/* ----------------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:		arm_q15_to_q7.c
*
* Description:	Converts the elements of the Q15 vector to Q7 vector.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* ---------------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupSupport
 */

/**
 * @addtogroup q15_to_x
 * @{
 */


/**
 * @brief Converts the elements of the Q15 vector to Q7 vector.
 * @param[in]       *pSrc points to the Q15 input vector
 * @param[out]      *pDst points to the Q7 output vector
 * @param[in]       blockSize length of the input vector
 * @return none.
 *
 * \par Description:
 *
 * The equation used for the conversion process is:
 *
 * <pre>
 * 	pDst[n] = (q7_t) pSrc[n] >> 8;   0 <= n < blockSize.
 * </pre>
 *
 */


void arm_q15_to_q7(
    q15_t *pSrc,
    q7_t *pDst,
    uint32_t blockSize)
{
    q15_t *pIn = pSrc;                             /* Src pointer */
    uint32_t blkCnt;                               /* loop counter */

#ifndef ARM_MATH_CM0_FAMILY

    /* Run the below code for Cortex-M4 and Cortex-M3 */
    q31_t in1, in2;
    q31_t out1, out2;

    /*loop Unrolling */
    blkCnt = blockSize >> 2u;

    /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
     ** a second loop below computes the remaining 1 to 3 samples. */
    while(blkCnt > 0u)
    {
        /* C = (q7_t) A >> 8 */
        /* convert from q15 to q7 and then store the results in the destination buffer */
        in1 = *__SIMD32(pIn)++;
        in2 = *__SIMD32(pIn)++;

#ifndef ARM_MATH_BIG_ENDIAN

        out1 = __PKHTB(in2, in1, 16);
        out2 = __PKHBT(in2, in1, 16);

#else

        out1 = __PKHTB(in1, in2, 16);
        out2 = __PKHBT(in1, in2, 16);

#endif //      #ifndef ARM_MATH_BIG_ENDIAN

        /* rotate packed value by 24 */
        out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24);

        /* anding with 0xff00ff00 to get two 8 bit values */
        out1 = out1 & 0xFF00FF00;
        /* anding with 0x00ff00ff to get two 8 bit values */
        out2 = out2 & 0x00FF00FF;

        /* oring two values(contains two 8 bit values) to get four packed 8 bit values */
        out1 = out1 | out2;

        /* store 4 samples at a time to destiantion buffer */
        *__SIMD32(pDst)++ = out1;

        /* Decrement the loop counter */
        blkCnt--;
    }

    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
     ** No loop unrolling is used. */
    blkCnt = blockSize % 0x4u;

#else

    /* Run the below code for Cortex-M0 */

    /* Loop over blockSize number of values */
    blkCnt = blockSize;

#endif /* #ifndef ARM_MATH_CM0_FAMILY */

    while(blkCnt > 0u)
    {
        /* C = (q7_t) A >> 8 */
        /* convert from q15 to q7 and then store the results in the destination buffer */
        *pDst++ = (q7_t) (*pIn++ >> 8);

        /* Decrement the loop counter */
        blkCnt--;
    }

}

/**
 * @} end of q15_to_x group
 */
